Thermal/fluid dynamics and liquid cooling a computer.

[SteveThing]

Hello all,

I am by no means a scientifically educated person. I am a network engineer by trade. As a hobby, I work on personal computers. That being said, I'm trying to find formulas for calculating what kind of cooling I can expect given a certain liquid cooling configuration.

What is commonly used for liquid cooling a typical home computer is water. This is due to the superior heat capacity of this material in comparison to other liquids/air. Some of the challenges with this are dealing with the corrosive nature of water depending on the pH balance. I'm trying to figure out how well mineral oil would work instead and what flow rate/PSI I would need to achieve to handle a thermal capacity of let's say... 125 thermal watts.

Typically, a computer's CPU generates far less than this. Some enthusiasts like to push the limits of their machines by overclocking. This obviously generates more heat. There have been some creative methods of dealing with this heat. So, on to the details:

Mass Specific Heat Capacities (Cp):
Distilled Water (25*C): 4.1813 kJ/kgK
Mineral Oil: 1.67 kJ/kgK
Copper: 0.385 kJ/kgK
Aluminium: 0.91 kJ/kgK

Viscosity in Centipoise(cP):
Distilled Water (25*C): 1 cP
Mineral Oil: 92 cP

So, given the above information, how would I figure out how much heat can be pulled off of a CPU with a copper block with water or mineral oil running through it at X flow rate? I know there are some variables missing, I just don't know what is needed...

Regards

 

[eljose79]

,

Hello,

I can provide some insight into your question about liquid cooling for a home computer. The first thing to consider is the specific heat capacity of the liquid being used. As you mentioned, water has a higher heat capacity compared to mineral oil, meaning it can absorb more heat before reaching its boiling point. This is why water is commonly used for liquid cooling in computers.

To calculate the amount of heat that can be pulled off a CPU using a specific liquid and flow rate, you will need to use the following formula:

Q = m * Cp * ΔT

Where:
Q = heat removed (in Joules)
m = mass flow rate (in kg/s)
Cp = specific heat capacity (in J/kgK)
ΔT = change in temperature (in K)

To find the mass flow rate, you will need to consider the volume flow rate (in m^3/s) and the density (in kg/m^3) of the liquid. The density of water is 1000 kg/m^3, while the density of mineral oil is around 900 kg/m^3.

As for the variables missing, you will also need to take into account the surface area of the copper block and the thermal conductivity of the materials involved. The higher the surface area and thermal conductivity, the more efficient the cooling will be.

I hope this helps you in your calculations. Let me know if you have any further questions.